Tuning means for an electrical musical instrument



Aug. 29, 1961 E. H. HILBORN TUNING MEANS FOR AN ELECTRICAL MUSICAL INSTRUMENT Filed Jan. 6, 1958 Unite f Stats This invention relates to electrical instruments embodying electronic oscillators for the production of tones.

Such principles have been applied to organs rather successfully, but for the most part, such instruments have usually required a separate tuned oscillator circuit for each musical note to be produced. Accordingly, for a normal tive octave keyboard electric organ having a foot manual, seventy-three oscillator circuits have been required, each necessitating separate adjustment to obtain the desired frequency. Then of course, there are some instruments capable of producing only a single tone at any one time irrespective of the number of keys which might be depressed. There have been many efforts directed towards simplification of these instruments as will be typitied by the disclosures of the patents to Hammond et al., 2,332,076, dated October i9, 1943; Haller et al., 2,505,182, dated April 25, 1950; and Schenau, 2,577,493, dated December 4, 1951.

In the Haller et al. patent, it was believed to be necessary to provide a tuning capacitor for each switch constituting a bank of switches under the control of each key on the keyboard. lt was with a view towards eliminating such a large number of tuning units because of their weight, cost and maintenance problems that the present invention was evolved.

Accordingly, it is among the objects of the present invention to provide in an electrical instrument, a plurality of keys, each corresponding to a musical note, a plurality of matched audio oscillators corresponding in number to the maximum number of musical notes to be produced simultaneously, a tuning unit corresponding to each oi the keys, the number of such tuning units corresponding to the number of keys, a plurality of interlocked switches corresponding to the number of oscillators actuated by each of the keys, and conductors interconnecting the tuning units, switches and oscillators whereby operation of a key establishes a circuit between its tuning unit and one of the oscillators. -Each tuning unit may comprise a resistor and in practice will probably include a variable capacitor as Well. The interlocked switches corresponding to one of the keys preferably includes a switch having a Contact connected in circuit with one of the oscillators when the key is depressed and with another of the oscillators when the key is retracted. The switches corresponding to one of the keys preferably has relatively movable contacts connected to the oscillators respectively, and each of `such switches is preferably of the single pole double throw variety. The switches corresponding to one of the keys preferably have one relatively fixed contact connected to the tuning unit and their remaining relatively xed contacts connected to relatively movable contacts of switches corresponding to another of the keys.

'It is also contemplated to provide in an electrical instrument, a plurality of matched audio frequency oscillators, a plurality of tuning units, a plurality of banks of switches for establishing circuits between the tuning units and the oscillators, a key controlling each bank of switches, a switch in each bank having a contact connected to a tuning unit and `a cooperating contact for establishing a circuit with at least one of the oscillators, the contacts being normally open, and a switch in each bank connected with a switch in a second bank selectively connecting a tuning unit with one of the oscillators. Here again, the number of tuning units will be equal to the arent number of keys. yIt is preferable that at least one switch in each bank have two relatively iixed contacts connected to relatively movable contacts of switches in another bank.

The invention is also characterized by the fact that actuation of a first switch means will connect a tirst tuning unit with one of the oscillators and simultaneously isolate this oscillator from a second tuning circuit, under which conditions, actuation of a second switch means will connect the second tuning circuit with another of the oscillators.

By virtue of the many advantages achieved, including savings in cost, reduction of size and weight, and appreciably smaller requirements for initial adjustment and maintenance, the present invention is adapted Jror use not only with permanently installed musical instruments, but with portable organs and smaller instruments such as accordions, as well.

A more complete understanding of the invention and its objects will follow from a detailed description with reference to the circuit diagram constituting the single iigure of the drawing.

The circuit depicted in the drawing represents an arrangement covering only a single octave and employing ve oscillators. ln practice, provision will be made for any desired number of octaves including half-notes and the number of oscillators will be determined by the maximum number of notes to be produced at any one time.

The keyboard depicted includes keys lil, 12, i4, i6, 18, 2t), 22 and 24 each of which is connected by means of an operator 26, shown in broken lines with the movable contact of each switch constituting its bank of switches. For example, depression of the key lil will shift the movable Contacts of its switches 10a, ltlb, lila', 10d and ltle from their upper contacts t0 their lower contacts, and release of the key 10 results in its return to its upper position by suitable spring biasing means which may be inherent by the use of leaf springs as the movable contacts.

Each of the switches under the control of the key 2f@- has its movable contact connected with an oscillator 30, 3?., 34, 36 and 38 respectively, whose output circuits 40 include blocking capacitors 42.

The lowermost switch of each bank has its lower contact connected with a tuning unit depicted as including a resistor 44 and a variable capacitor 46. The tuning units for the keys lil, l2, 14, 16, 218, 2t), 22 and 24 have been designated 4S, Sil, 52, 54, 56, 58, 6i) and 62 respectively. l

Referring to the switches under the control of the key 1t), each movable contact is connected to one or more fixed contacts of the switches of the adjacent bank under the control of the key l2. iAs already indicated, the lower contact of the lowermost switch ltle is connected to its tuning unit 43. The remaining fixed contacts ofthe switches under the control of the key it) are connected to a common conductor 64 which is grounded. The lower terminals of the tuning units are also connected to ground by means of a conductor 66.

Referring to the switches under the control of the key 24. each movable Contact is connected to the input of one of the oscillators. The lower contact of the lowermost switch 24e of this bank is connected to its tuning unit 6?., the other xed contacts of the switches of this bank are connected to movable contacts of the switches in an adjacent bank under the control of the key 22.

inasmuch as the oscillators are all matched so that any one oi them will produce any of the notes represented by the various keys, the circuit details of the oscillator 38 have been shown as typical of them all. Various types of oscillators can be substituted for that shown, so long as they can be matched. The matching of the oscillators will be etected to a degree that will produce the desired musical elects, and it is contemplated that matching of the o-rder of plus or minus 0.5% will be adequate for most purposes.

The B-I- supply is connected to each of the oscillators, depicted by way of example, through a conductor 68 leading to an isolating resistor 70 which is isolated from ground through an isolating capacitor 72. The common terminals of the resistor 70 and capacitor 72 are connected to a variable resistor 74 whose adjustable tap is connected to the anode 76 of a vacuum tube 78 through the primary winding of a feedback coupling transformer 30. The secondary of this transformer is connected to the control electrode S2 of the vacuum tube through a capacitor 8a with which a variable capacitor 36 is in parallel. The control grids of the various tubes are connected with the movable contacts of the switches under the control of the key 24 by means of conductors S8.

The cathode 90 of each tube is grounded through a resistor 92. The several oscillators are matched by adjustment of their variable resistors 74 and their variable capacitors 86 so that each will produce the same sound when its input is connected with any one of the several tuning units. The pitch produced by depression of each key is determined by its tuning unit, each containing a resistor 44 and a variable capacitor 46. The approximate pitch is determined by the value of the resistor, the variable capacitor permitting a fine adjustment which may be about a full tone on the musical scale. Theoretically, the resistor 41?, could be selected so as to produce the desired note without the need for the variable capacitor. In practice however, it is probable that the capacitor will be employed as well.

Whereas various values may be assigned to the components of a circuit embodying the present invention, it may be well to recite values that have been used in one embodiment. The variable capacitor $6 had a range of from 30 to 250 micromicrofarads, the capacitor 84 had a value of 0.001 microfarad, the capacitor 46 had a range of from 20 to 100 micromicrofarads, the capacitor 42 had a value of 0.005 microfarad, and the capacitor 72 had a value of 0.1 microfarad. The resistor 74 had a maximum value of 25,000 ohms, the resistor 70 had a value of 250,000 ohms and the resistor 44 had a resistance of from 100,000 to 2,000,000 ohms. The transformer S had a 3:1 ratio, the B-lvoltage was 150 volts and the vacuum tubes 78 were of the 12AX7 type.

In operation, when one of the keys is depressed, the movable contacts of its several switches move from their upper fixed contacts to their lower ixed contacts establishing a circuit to one of the oscillators and readying the circuits of the remaining oscillators for the depression of other keys. Thus, assuming that the key 22 has been depressed, its lower switch 22e will establish a circuit between its tuning unit 60 and the oscillator 3S to produce a musical sound represented by the key 22. The other oscillators will be connected to ground through the various switches and the common conductor 64 so that only the oscillator 3% will produce an audible signal through the output system of the instrument. Assuming that the key 22 remains depressed and another of the keys, say key 18, is also depressed, a circuit will be established through the tuning unit 56 and the oscillator 36 through the switches 18e, 20e, 22d and 24d to produce a second musical sound. lf a third key, such as the key 14 is also depressed, its tuning unit 52 will be connected with the oscillator 34 through the switches 14e, 16e, 18d, 20d, 22C and 24C. Thus, since the number of oscillators employed is equal to the number of notes to be produced simultaneously, it will follow that each bank of switches will contain one switch for each oscillator and for each bank of switches there will be only one tuning unit.

It will be understood by those skilled in the art, that the contacts which have been described as fixed may be rendered movable and those described as movable may be xed without departing from the concept or results proposed.

In view of the simplification of electrical musical instruments made possible by the present invention, it is well adapted for use with portable instruments such as accordions, as well as with electric organs and other instruments ordinarily conned to a particular location.

Whereas only one speciic form of the invention has been shown and described, various modifications are contemplated within the scope of the appended claims.

I claim:

l. In an electrical musical instrument, a plurality of keys each corresponding to a musical sound, a plurality of matched electronic audio oscillators corresponding in number to the maximum number of musical notes to be produced simultaneously, a bank of double throw switches actuated by each of said keys, the number of switches in each bank corresponding to the number of said oscillators, and tuning means for each said bank; said switches in a first one of said banks having relatively movable contacts connected to said oscillators respectively, one switch in said rst bank having a relatively fixed contact connected to its tuning means, the remaining relatively iixed contacts of the switches in said first bank being connected to a relatively movable contacts of switches in an adjacent bank; and said switches in a second of said banks having relatively movable contacts connected to relatively xed contacts of switches in an adjacent bank, one switch of said second bank having a relatively fixed contact connected to its tuning means, and its remaining relatively iixed contacts connected to a common conductor, whereby any of said oscillators responds to any of said keys, but only one of said oscillators responds to only one of said keys at any one time.

2. In an electrical instrument, a plurality of keys each corresponding to a musical note, a plurality of matched audio oscillators corresponding in number to the maximum number of musical notes to be produced simultaneously, a tuning unit corresponding `to each of said keys, the number of such tuning units corresponding to the number of said keys, a plurality of interlocked switches corresponding to the number of said oscillators actuated by each of said keys, and conductors interconnecting said tuning units, switches and oscillators whereby operation of a key establishes a circuit between its said tuning unit and any one of said oscillators exclusively.

3. In an electrical instrument as set forth in claim 2 wherein said tuning unit comprises a resistor.

4. In an electrical instrument as set forth in claim 2 wherein said tuning unit comprises a capacitor.

5. In an electrical instrument as set forth in claim 2 wherein said turing unit comprises an impedance.

6. In an electrical instrument as' set forth in claim 2 wherein the interlocked switches corresponding to one of said keys includes a switch having a contact connected in circuit with one of said oscillators when said key is depressed and with another of said oscillators when said key is retracted.

7. In an electrical instrument as set forth in claim 2 wherein each of said switches is of the single pole double throw type.

8. In an electrical instrument as set forth in claim 7 wherein said switches corresponding to one of said keys have relatively movable contacts connected to said os'cillators respectively.

9. In an electrical instrument as set forth in claim 7 wherein said switches corresponding to one of said keys have one relatively iixed contact connected to said tuning unit and remaining relatively lixed contacts connected to movable contacts of switches corresponding to another of said keys.

10. In an electrical instrument, a plurality of matched audio frequency oscillators, a plurality of tuning units, a plurality of banks of switches each comprising a plurality of switches for establishing circuits between said tuning units and said oscillators, a key controlling each bank of switches', a switch in each bank having a iixed contact connected to a tuning unit and a cooperating contact for establishing a circuit with at least one of said oscillators, said contacts being normally open, and the remaining switches in each bank having their iXed contacts connected with a switch in a second bank selectively connecting a tuning unit with any one of said oscillators exclusively.

ll. In an electrical instrument as set forth in claim 10 wherein the number of tuning units is equal tothe number of keys.

12. In an electrical instrument as set forth in claim l() wherein a switch in each bank has two relatively iXed contacts connected to relatively movable contacts of switches in another bank.

13. In an electrical musical instrument having an output system, a plurality of matched electronic oscillators, a keyboard having rst and second keys corresponding to unlike musical sounds, a rst switch means including a plurality of switches operated by said iirst key, a first tuning circuit connected to one of said switches for connection in circuit with one of said oscillators each time said first key is actuated, a second switch means including a plurality of switches operated by said second key, and a second tuning circuit connected to one of said switches of said second switch means for connection in circuit with one of said oscillators each time said second key is actuated, there being only one such tuning circuit corresponding to each said key, actuation of said first switch means connecting said rst tuning circuit with one of said oscillators exclusively and simultaneously isolating said one oscillator from said second tuning circuit, under which conditions, actuation of said second switch means con nects said second tuning circuit with another of said oscillators exclusively.

References Cited in the le of this patent UNITED STATES PATENTS y2,505,182 Haller et al Apr. 25, 1950 2,848,919 Hanert Aug. 26, 1958 2,905,905 George Sept. 22, 1959 FOREIGN PATENTS 153,660 Austria June 25, 1938 

